Identification and characterisation of the tegument-expressed aldehyde dehydrogenase SmALDH_312 of Schistosoma mansoni, a target of disulfiram.

Schistosomiasis is an infectious disease caused by blood flukes of the genus Schistosoma and affects approximately 200 million people worldwide. Since Praziquantel (PZQ) is the only drug for schistosomiasis, alternatives are needed. By a biochemical approach, we identified a tegumentally expressed aldehyde dehydrogenase (ALDH) of S. mansoni, SmALDH_312. Molecular analyses of adult parasites showed Smaldh_312 transcripts in both genders and different tissues. Physiological and cell-biological experiments exhibited detrimental effects of the drug disulfiram (DSF), a known ALDH inhibitor, on larval and adult schistosomes in vitro. DSF also reduced stem-cell proliferation and caused severe tegument damage in treated worms. In silico-modelling of SmALDH_312 and docking analyses predicted DSF binding, which we finally confirmed by enzyme assays with recombinant SmALDH_312. Furthermore, we identified compounds of the Medicine for Malaria Venture (MMV) pathogen box inhibiting SmALDH_312 activity. Our findings represent a promising starting point for further development towards new drugs for schistosomiasis.

Identification of a new panel of reference genes to study pairing-dependent gene expression in Schistosoma mansoni.

Facilitated by the Schistosoma mansoni genome project, multiple transcriptomic studies were performed over the last decade to elucidate gene expression patterns among different developmental stages of the complex schistosome life cycle. While these analyses enable the identification of candidate genes with key functions in schistosome biology, a diverse molecular tool set is needed that allows comprehensive functional characterization at the single gene level. This includes the availability of reliable reference genes to confirm changes in the transcription of genes of interest over different biological samples and experimental conditions. In particular, the investigation of one key aspect of schistosome biology, the pairing-dependent gene expression in females and males, requires knowledge on reference genes that are expressed independently of both pairing and of in vitro culture effects. Therefore, the present study focused on the identification of quantitative reverse transcription (qRT)-PCR reference genes suitable for the investigation of pairing-dependent gene expression in the S. mansoni male. The "pipeline" we present here is based on qRT-PCR analyses of high biological replication combined with three different statistical analysis tools, BestKeeper, geNorm, and NormFinder. Our approach resulted in a statistically robust ranking of 15 selected reference genes with respect to their transcription stability between pairing-unexperienced and -experienced males. We further tested the top seven candidate genes for their transcription stability during invitro culture of adult S. mansoni. Of these, the two most suitable reference genes were used to investigate the influence of the pairing contact on the transcription of genes of interest, comprising a tyrosine decarboxylase gene Smtdc1, an ebony ortholog Smebony, and the follistatin ortholog Smfst in S. mansoni males. Performing pairing, separation and re-pairing experiments with adult S. mansoni in vitro, our results indicate for the first time that pairing can act as a molecular on/off-switch of specific genes to strictly control their expression in schistosome males.

Biarylalkyl Carboxylic Acid Derivatives as Novel Antischistosomal Agents.

Parasitic platyhelminths are responsible for serious infectious diseases, such as schistosomiasis, which affect humans as well as animals across vast regions of the world. The drug arsenal available for the treatment of these diseases is limited; for example, praziquantel is the only drug currently used to treat ≥240 million people each year infected with Schistosoma spp., and there is justified concern about the emergence of drug resistance. In this study, we screened biarylalkyl carboxylic acid derivatives for their antischistosomal activity against S. mansoni. These compounds showed significant influence on egg production, pairing stability, and vitality. Tegumental lesions or gut dilatation was also observed. Substitution of the terminal phenyl residue in the biaryl scaffold with a 3-hydroxy moiety and derivatization of the terminal carboxylic acid scaffold with carboxamides yielded compounds that displayed significant antischistosomal activity at concentrations as low as 10 µm with satisfying cytotoxicity values. The present study provides detailed insight into the structure-activity relationships of biarylalkyl carboxylic acid derivatives and thereby paves the way for a new drug-hit moiety for fighting schistosomiasis.

Derivatives of biarylalkyl carboxylic acid induce pleiotropic phenotypes in adult Schistosoma mansoni in vitro.

Schistosomes and other parasitic platyhelminths cause infectious diseases of worldwide significance for humans and animals. Despite their medical and economic importance, vaccines are not available and the number of drugs is alarmingly limited. For most platyhelminths including schistosomes, Praziquantel (PZQ) is the commonly used drug. With respect to its regular application in mass treatment programs, however, there is increasing concern about resistance development.Previous studies demonstrated that inhibitors used to treat non-parasitic human diseases may be useful to be tested for their effects on parasites. To this end, we focused on biarylalkyl carboxylic acids (BACAs) as basis, which had been shown before to be interesting candidates in the context of finding alternative approaches to treat diabetes mellitus. We tested 32 chemically modified derivatives of these substances (biarylalkyl carboxylic acid derivatives (BACADs)) for their effects on adult Schistosoma mansoni in vitro. Treatment with 18 BACADs resulted in egg production-associated phenotypes and reduced pairing stability. In addition, 12 of these derivatives affected vitality and/or caused severe tegument damage, gut dilatation, or other forms of tissue disintegration which led to the death of worms. In most cases (10/12), one derivative caused more than one phenotype at a time. In vitro experiments in the presence of serum albumin (SA) and alpha-acidic glycoprotein (AGP) indicated a varying influence of these blood components on the effects of two selected derivatives. The variety of observed phenotypes suggested that different targets were hit. The results demonstrated that BACADs are interesting substances with respect to their anti-schistosomal effects.

Inhibitory activities of the marine streptomycete-derived compound SF2446A2 against Chlamydia trachomatis and Schistosoma mansoni.

Infectious diseases caused by chlamydia or schistosomes are a major health problem worldwide, and particularly so in developing countries. The lack of appropriate vaccines renders the search for potent natural products against these disease-causing agents an urgent endeavor. Sponge-associated actinomycetes represent a rich reservoir for natural products. Among them, members of the genus Streptomyces are capable of synthesizing an impressive array of diverse natural products with a wide variety of biological activities. The naphthacene glycoside SF2446A2 was isolated from the calcium alginate beads culture of Streptomyces sp. strain RV15 that had originally been obtained from the Mediterranean sponge Dysidea tupha. Its structure was identified by spectroscopic analysis and MS and comparison with the literature data. SF2446A2 showed inhibitory activity against Chlamydia trachomatis and was able to inhibit the primary infection in a dose-dependent manner, as well as progeny formation. Moreover, it caused disruptive effects on the surface area of Schistosoma mansoni and affected the gonads by impairing oogenesis and spermatogenesis. Our current study demonstrates that sponge-associated actinomycetes are capable of providing compounds with new pharmacological activities and with relevance to drug discovery.